Three contingency conditions were applied to the math performance of 4th and 5th graders: bonus credit for accurately solving math problems, bonus credit for completing math problems, and no bonus credit for accurately answering or completing math problems. Mixed ANOVAs were used in tracking the performance of high, medium, and low performers during the experimental phase across a mandatory follow-up phase and a choice follow-up phase. The two reward contingencies produced generally higher performance than the non-reward contingency (control condition) in the experimental phase, but all performance levels did better in the mandatory follow-up phase after the non-reward condition than after either reward contingency. Plus, high performers did substantially better in the choice phase following a non-reward contingency than following either reward contingency, most especially following the accuracy contingency. The pattern of results generally points to an overjustification effect for contingent bonus credit, with this effect more attributable to a perception of control than a perception of competency.